Formal Synthesis of Bioactive Indole Alkaloids Eburnamonine, Eburnaminol, and Vindeburnol

Starting from (+/-)-3-acetoxyglutarimide, diastereoselective formal synthesis of indole alkaloids (+/-)-eburnamonine, (+/-)-eburnaminol, and (+/-)-vindeburnol have been demonstrated via a common intermediate (+/-)-1-hydroxy-12-tosyl-2,3,6,7,12,12b-hexahydroindolo[2,3a] quinolizin-4(1H)-one in very good overall yields. The acetoxy group from (+/-)-3-acetoxyglutarimide was first used to induce the diastereoselectivity and also as a latent source of ketone carbonyl group. The stereoselective eliminations, reductions, and intramolecular cyclizations were the involved key steps.